Terahertz quantum cascade lasers based on interface roughness engineering in InGaAs/InAlAs heterostructures on InP

• Applicant: Professor Dr. William Ted Masselink
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2014 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 248490517

The objective of this research is to demonstrate and investigate terahertz quantum cascade lasers based on a novel InGaAs-based active region. Indications are that lasers using this new design will operate near room-temperature; operation of THz QCLs at such high temperatures has not yet been demonstrated and would represent a revolutionary advance for terahertz instrumentation, opening new possibilities in terahertz research and applications.The proposed active region is the InGaAs/ InGaAs strain-compensated material system on InP. Both components of this material system are members of the well-established InGaAs alloy family on InP. By compensating the compressive strain of the InGaAs with In content less than 0.53 with the tensile strain of the InGaAs with In content greater than 0.53, strain-compensated structures with arbitrarily low conduction band offset can be realized using molecular beam epitaxy. The application of this system for THz QCLs has been described in a patent disclosure.The advantage of InGaAs/ InGaAs material system over GaAs/AlGaAs is the smaller electron effective mass in the quantum wells. Because of the higher laser gain associated with smaller electron effective mass, the proposed terahertz lasers are expected to have approximately 2.3 times higher gain and be able to operate at temperatures at least 100 K higher than is possible with the current state-of-the art GaAs/Al0.15Ga0.85As devices. Furthermore, the smaller effective mass in the proposed devices is expected to result in reduced interface roughness scattering and higher electron mobility that will further improve their performance.The advantage of the strain-compensated InGaAs material system over the lattice-matched InGaAs/InAlAs (or InGaAs/GaAsSb) material systems on InP for terahertz quantum cascade lasers is the possibility to choose the appropriate optimal conduction band offset in the range of 130 to 150 meV, in contrast to the high conduction band offset of 520 meV in the lattice matched InGaAs/InAlAs on InP or 360 meV in the lattice matched InGaAs/GaAsSb on InP.We expect that these improvements will allow us to create terahertz semiconductor lasers that can operate at near room temperature. We finally note that, unlike other approaches that are being suggested to improve the temperature performance of terahertz quantum cascade lasers, the proposed approach is a radical departure from established THz QCL approaches, but has the advantage that it relies on well-established growth techniques and material systems.

• DFG Programme: Research Grants